Potential Persistence via Time Provider Modification

Identifies modification of the Time Provider. Adversaries may establish persistence by registering and enabling a malicious DLL as a time provider. Windows uses the time provider architecture to obtain accurate time stamps from other network devices or clients in the network. Time providers are implemented in the form of a DLL file which resides in the System32 folder. The service W32Time initiates during the startup of Windows and loads w32time.dll.

Elastic rule (View on GitHub)

  1[metadata]
  2creation_date = "2021/01/19"
  3integration = ["endpoint"]
  4maturity = "production"
  5min_stack_comments = "New fields added: required_fields, related_integrations, setup"
  6min_stack_version = "8.3.0"
  7updated_date = "2024/03/28"
  8
  9[transform]
 10[[transform.osquery]]
 11label = "Osquery - Retrieve DNS Cache"
 12query = "SELECT * FROM dns_cache"
 13
 14[[transform.osquery]]
 15label = "Osquery - Retrieve All Services"
 16query = "SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services"
 17
 18[[transform.osquery]]
 19label = "Osquery - Retrieve Services Running on User Accounts"
 20query = """
 21SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services WHERE
 22NOT (user_account LIKE '%LocalSystem' OR user_account LIKE '%LocalService' OR user_account LIKE '%NetworkService' OR
 23user_account == null)
 24"""
 25
 26[[transform.osquery]]
 27label = "Osquery - Retrieve Service Unsigned Executables with Virustotal Link"
 28query = """
 29SELECT concat('https://www.virustotal.com/gui/file/', sha1) AS VtLink, name, description, start_type, status, pid,
 30services.path FROM services JOIN authenticode ON services.path = authenticode.path OR services.module_path =
 31authenticode.path JOIN hash ON services.path = hash.path WHERE authenticode.result != 'trusted'
 32"""
 33
 34[rule]
 35author = ["Elastic"]
 36description = """
 37Identifies modification of the Time Provider. Adversaries may establish persistence by registering and enabling a
 38malicious DLL as a time provider. Windows uses the time provider architecture to obtain accurate time stamps from other
 39network devices or clients in the network. Time providers are implemented in the form of a DLL file which resides in the
 40System32 folder. The service W32Time initiates during the startup of Windows and loads w32time.dll.
 41"""
 42from = "now-9m"
 43index = ["logs-endpoint.events.registry-*", "endgame-*", "logs-windows.sysmon_operational-*"]
 44language = "eql"
 45license = "Elastic License v2"
 46name = "Potential Persistence via Time Provider Modification"
 47note = """## Triage and analysis
 48
 49### Investigating Potential Persistence via Time Provider Modification
 50
 51The Time Provider architecture in Windows is responsible for obtaining accurate timestamps from network devices or clients. It is implemented as a DLL file in the System32 folder and is initiated by the W32Time service during Windows startup. Adversaries may exploit this by registering and enabling a malicious DLL as a time provider to establish persistence. 
 52
 53This rule identifies changes in the registry paths associated with Time Providers, specifically targeting the addition of new DLL files.
 54
 55> **Note**:
 56> This investigation guide uses the [Osquery Markdown Plugin](https://www.elastic.co/guide/en/security/master/invest-guide-run-osquery.html) introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.
 57
 58### Possible investigation steps
 59
 60- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
 61- Investigate other alerts associated with the user/host during the past 48 hours.
 62- Examine whether the DLL is signed.
 63- Retrieve the DLL and determine if it is malicious:
 64  - Analyze the file using a private sandboxed analysis system.
 65  - Observe and collect information about the following activities in both the sandbox and the alert subject host:
 66    - Attempts to contact external domains and addresses.
 67      - Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process' `process.entity_id`.
 68      - Examine the DNS cache for suspicious or anomalous entries.
 69        - $osquery_0
 70    - Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
 71    - Examine the host services for suspicious or anomalous entries.
 72      - $osquery_1
 73      - $osquery_2
 74      - $osquery_3
 75  - Retrieve the files' SHA-256 hash values using the PowerShell `Get-FileHash` cmdlet and search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
 76
 77### False positive analysis
 78
 79- This activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.
 80
 81### Response and Remediation
 82
 83- Initiate the incident response process based on the outcome of the triage.
 84- Isolate the involved host to prevent further post-compromise behavior.
 85- If the triage identified malware, search the environment for additional compromised hosts.
 86  - Implement temporary network rules, procedures, and segmentation to contain the malware.
 87  - Stop suspicious processes.
 88  - Immediately block the identified indicators of compromise (IoCs).
 89  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
 90- Remove and block malicious artifacts identified during triage.
 91- Restore Time Provider settings to the desired state.
 92- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
 93- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business systems, and web services.
 94- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
 95- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
 96"""
 97references = ["https://pentestlab.blog/2019/10/22/persistence-time-providers/"]
 98risk_score = 47
 99rule_id = "14ed1aa9-ebfd-4cf9-a463-0ac59ec55204"
100severity = "medium"
101tags = ["Domain: Endpoint", "OS: Windows", "Use Case: Threat Detection", "Tactic: Persistence", "Tactic: Privilege Escalation", "Data Source: Elastic Endgame", "Data Source: Elastic Defend", "Data Source: Sysmon"]
102timestamp_override = "event.ingested"
103type = "eql"
104
105query = '''
106registry where host.os.type == "windows" and event.type:"change" and
107  registry.path: (
108    "HKLM\\SYSTEM\\*ControlSet*\\Services\\W32Time\\TimeProviders\\*",
109    "\\REGISTRY\\MACHINE\\SYSTEM\\*ControlSet*\\Services\\W32Time\\TimeProviders\\*"
110  ) and
111  registry.data.strings:"*.dll" and
112  not
113  (
114    process.executable : "?:\\Windows\\System32\\msiexec.exe" and
115    registry.data.strings : "?:\\Program Files\\VMware\\VMware Tools\\vmwTimeProvider\\vmwTimeProvider.dll"
116  )
117'''
118
119
120[[rule.threat]]
121framework = "MITRE ATT&CK"
122[[rule.threat.technique]]
123id = "T1547"
124name = "Boot or Logon Autostart Execution"
125reference = "https://attack.mitre.org/techniques/T1547/"
126[[rule.threat.technique.subtechnique]]
127id = "T1547.003"
128name = "Time Providers"
129reference = "https://attack.mitre.org/techniques/T1547/003/"
130
131
132
133[rule.threat.tactic]
134id = "TA0003"
135name = "Persistence"
136reference = "https://attack.mitre.org/tactics/TA0003/"
137
138[[rule.threat]]
139framework = "MITRE ATT&CK"
140[[rule.threat.technique]]
141id = "T1547"
142name = "Boot or Logon Autostart Execution"
143reference = "https://attack.mitre.org/techniques/T1547/"
144[[rule.threat.technique.subtechnique]]
145id = "T1547.003"
146name = "Time Providers"
147reference = "https://attack.mitre.org/techniques/T1547/003/"
148
149
150
151[rule.threat.tactic]
152id = "TA0004"
153name = "Privilege Escalation"
154reference = "https://attack.mitre.org/tactics/TA0004/"

Triage and analysis

Investigating Potential Persistence via Time Provider Modification

The Time Provider architecture in Windows is responsible for obtaining accurate timestamps from network devices or clients. It is implemented as a DLL file in the System32 folder and is initiated by the W32Time service during Windows startup. Adversaries may exploit this by registering and enabling a malicious DLL as a time provider to establish persistence.

This rule identifies changes in the registry paths associated with Time Providers, specifically targeting the addition of new DLL files.

Note: This investigation guide uses the Osquery Markdown Plugin introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.

Possible investigation steps

  • Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
  • Investigate other alerts associated with the user/host during the past 48 hours.
  • Examine whether the DLL is signed.
  • Retrieve the DLL and determine if it is malicious:
    • Analyze the file using a private sandboxed analysis system.
    • Observe and collect information about the following activities in both the sandbox and the alert subject host:
      • Attempts to contact external domains and addresses.
        • Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process' process.entity_id.
        • Examine the DNS cache for suspicious or anomalous entries.
          • $osquery_0
      • Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
      • Examine the host services for suspicious or anomalous entries.
        • $osquery_1
        • $osquery_2
        • $osquery_3
    • Retrieve the files' SHA-256 hash values using the PowerShell Get-FileHash cmdlet and search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.

False positive analysis

  • This activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.

Response and Remediation

  • Initiate the incident response process based on the outcome of the triage.
  • Isolate the involved host to prevent further post-compromise behavior.
  • If the triage identified malware, search the environment for additional compromised hosts.
    • Implement temporary network rules, procedures, and segmentation to contain the malware.
    • Stop suspicious processes.
    • Immediately block the identified indicators of compromise (IoCs).
    • Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
  • Remove and block malicious artifacts identified during triage.
  • Restore Time Provider settings to the desired state.
  • Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
  • Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business systems, and web services.
  • Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
  • Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).

References

Related rules

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